Cholesterol-lowering "dietary supplements" pose serious problems. ConsumerLab.com has found that the amounts of the cholesterol-lowering substance in ten red yeast rice products sold as dietary supplements varied by more than 100-fold, with some products providing as much as prescription medication and others containing very little. The tests also found that four of the products contained citrinin, which can cause kidney damage. [Product review: Red yeast rice supplements. ConsumerLab.Com, July 18, 2008] Red yeast rice contains the cholesterol-lowering statin compound lovastatin, the active ingredient in prescription Mevacor. Although lovastatin is a very useful drug, it is not suitable for self-medication because optimal cholesterol-control should be tailored to individual risk factors and be medically monitored. The FDA has ordered at least eight marketers to stop marketing red yeast rice products for cholesterol control. However, the Dietary Supplement Health and Education Act of 1994 permits their sale as "dietary supplements."

Study finds vitamin C interferes with anti-cancer drugs. Laboratory studies have found that vitamin C may interfere with the effectiveness of five anti-cancer drugs. First, the researchers gave a vitamin C product to cancer cells that were treated with chemotherapy and found that the 30% to 70% fewer cancer cells were killed. Then they injected mice with cancer cells, administered chemotherapy, and found that cells grew into tumors much faster in the mice that received pre-treatment vitamin C. The researchers warned that although results in animals are not necessarily applicable to humans, vitamin C supplementation during cancer treatment may interfere with the effect of chemotherapy. [Heaney ML and others. Vitamin C antagonizes the cytotoxic effects of antineoplastic drugs. Cancer Research 68:8031-8038, 2008] This study reinforces doubts that vitamin C will find practical use as a cancer drug. [Barrett S. High doses of vitamin C are not
effective as a cancer treatment. Quackwatch, Oct 24, 2008]